Method of purifying acetic anhydride



Patented Sept. 4, 1923.

UNITED STATES PATENT OFFICE.

CHARLES J'- STBOSACKEB AND CLARENCE C. SCHWEGLER, OF MIDLAND, IICHIGLN,

ASSIGNOBS TO THE DOW CHEMICAL COIPAHY, F MIDLAND, MICHIGAN,

rom'rron or nemesis.

ACOR- METHOD OF PUBIFYING ACETIC Io Drawing.

To all whom it may conce'm:

Be it known that we, CHARLES J. S'rno- SACKER and CLARENCE O. Sonwnomn, citizens of the United States, and residents of Midland, county of Midland,

State of Michigan, have jointly invented a new and useful Improvement in Methods of Purifying ,Acetic Anhydride, which the following-ism. specification, the

principle of the in vention being herein explained and the best contemplated applying that principle, so as to distinguish-it from other inventions. Acetic anhydride (GIL-CO) 0, as is well known, is, a reagent of great importance in the manufacture of organic compounds particularly for converting primary and secondary aminesinto acetyl derivatlves.- As an incident of its manufacture, the commercial article, however, is almost always found to contain some sulphur, this sulphur beipg mainl in the form of. thio .anhydride,

(C ,.CO), which impurity is objectionable in connection with the use of acetic anhydride, and at the same time extremely diflicult to eliminate, since its boiling point and that of such anhydride are substantially identical. The object of the presentinvention is to provide a simple and convenient process'for the purification of acetic anhy pounds in question. To this tion consists of the steps hereinafter fully described and particularl the claims; the following descriptionsetting however, constituting but one of the various ways in which the principle of the invention may be used.

out our improved rooess'we rate or bromate, or with a metallic oxide,

mode in which we have .dride by the elimination of the sulphur com-' end the invenpointed out in forth-in detail an approved mode of carrying out the invention, such disclosed mode,

'In ca treat the crude acetic anhydride with a chlo- Application filed November is, 1918. Serial 10.282386.

preferably manganese oxide. Since such crude acetic anhydride requires to be re-v distilled in. order to eliminate other impurities, we find it convenient to introduce the reagent, thus designed to eliminate the sulphur, at this stage, mixin it with the anhydride as it is introduced mto the still. All of the reagents named are insoluble in the anhydride but readily unite with any sulphur compounds 'that may be present. The I amount of the reagent added will be gauged to correspondwith theamount of the sulphur as previously determined. s

Other modes of applying the principle of our invention maybe employed instead of the one explained, change being made as 'regards the method herein disclosed, provided the step or steps stated by any of the fol lowing claims or' the equivalent of such stated step or steps'be employed. -We therefore particularly point out and l distinctly claim as our invention 1. Ima method of purifying acetic anhydride containing a sulphur compound of approximately the same boiling point as an impurity, the steps which consist in' introducin 'intosuch anhydride a; metallic oxide insolu le' therein but capable of readily unitmg with such sulphur compound, and then distilling. p

2. In a method of purifying acetic anhydride containing a sulphur-compound of approximatelythe same boiling point as an impurity, the steps which consist in introducing into such anhydride an oxide ofmanganese insoluble therein but capable of readily uniting with such sulphur compound, and then distilling. 19figned .by us, this 8th'day .of November,

' CHARLES J. STROSACKER. CLARENCE o. SCHWEGLER. 

